Lessons Learned From the First-In-Human Compassionate Use of Connect-EA™ in Ten Patients With Esophageal Atresia.

INTRODUCTION: Delayed primary repair of esophageal atresia in patients with high-risk physiologic and anatomic comorbidities remains a daunting challenge with an increased risk for peri-operative morbidity and mortality via conventional repair. The Connect-EA device facilitates the endoscopic creation of a secure esophageal anastomosis. This follow-up study reports our long-term outcomes with the novel esophageal magnetic compression anastomosis (EMCA) Connect-EA device for EA repair, as well as lessons learned from the ten first-in-human cases. We propose an algorithm to maximize the advantages of the device for EA repair. METHODS: Under compassionate use approval, from June 2019 to December 2022, ten patients with prohibitive surgical or medical risk factors underwent attempted EMCA with this device. All patients underwent prior gastrostomy, tracheoesophageal fistula ligation (if necessary), and demonstrated pouch apposition prior to EMCA. RESULTS: Successful device deployment and EMCA formation were achieved in nine patients (90%). Mean time to anastomosis formation was 8 days (range 5-14) and the device was retrieved endoscopically in five (56%) cases. At median follow-up of 22 months (range 4-45), seven patients (78%) are tolerating oral nutrition. Balloon dilations (median 4, range 1-11) were performed either prophylactically for radiographic asymptomatic anastomotic narrowing (n = 7, 78%) or to treat clinically-significant anastomotic narrowing (n = 2, 22%) with no ongoing dilations at 3-month follow up post-repair. CONCLUSION: EMCA with the Connect-EA device is a safe and feasible minimally-invasive alterative for EA repair in high-risk surgical patients. Promising post-operative outcomes warrant further Phase I investigation. LEVEL OF EVIDENCE: IV, Case series of novel operative technique without comparison group.

The novel application of an emerging device for salvage of primary repair in high-risk complex esophageal atresia.

INTRODUCTION: Preservation of native esophagus is a tenet of esophageal atresia (EA) repair. However, techniques for delayed primary anastomosis are severely limited for surgically and medically complex patients at high-risk for operative repair. We report our initial experience with the novel application of the Connect-EA, an esophageal magnetic compression anastomosis device, for salvage of primary repair in 2 high-risk complex EA patients. Compassionate use was approved by the FDA and treating institutions. OPERATIVE TECHNIQUE: Two approaches using the Connect-EA are described - a totally endoscopic approach and a novel hybrid operative approach. To our knowledge, this is the first successful use of a hybrid operative approach with an esophageal magnetic compression device. OUTCOMES: Salvage of delayed primary anastomosis was successful in both patients. The totally endoscopic approach significantly reduced operative time and avoided repeat high-risk operation. The hybrid operative approach salvaged delayed primary anastomosis and avoided cervical esophagostomy. CONCLUSION: The Connect-EA is a novel intervention to achieve delayed primary esophageal repair in complex EA patients with high-risk tissue characteristics and multi-system comorbidities that limit operative repair. We propose a clinical algorithm for use of the totally endoscopic approach and hybrid operative approach for use of the Connect-EA in high-risk complex EA patients.

Epidemiology of pediatric trauma during the COVID-19 pandemic shelter in place.

INTRODUCTION: The first COVID-19 cases occurred in the US in January of 2020, leading to the implementation of shelter in place. This study seeks to define the impact of shelter in place on the epidemiology of pediatric trauma. METHODS: We examined pediatric trauma admissions at 5 Level 1 and 1 Level 2 US pediatric trauma centers between January 1 and June 30, 2017-2020. Demographic and injury data were compared between pre- and post-shelter in place patient cohorts. RESULTS: A total of 8772 pediatric trauma activations were reviewed. There was a 13% decrease in trauma volume in 2020, with a nadir at 16 days following implementation of shelter in place. Injury severity scores were higher in the post-shelter in place cohort. The incidence of nonmotorized vehicle accidents and gunshot wounds increased in the post-shelter in place cohort. CONCLUSION: We found an overall decrease in pediatric trauma volume following shelter in place. However, injuries tended to be more severe. Our findings help inform targeted injury prevention campaigns during future pandemics.

A comparison of accidental and nonaccidental trauma: it is worse than you think.

BACKGROUND: Child abuse, or nonaccidental trauma (NAT), is a major cause of pediatric morbidity and mortality, and is often unrecognized. Our hypothesis was that injuries due to accidental trauma (AT) and NAT are significantly different in incidence, injury, severity, and outcome, and are often unrecognized. OBJECTIVE: Our aim was to carry out an examination of the differences between pediatric injuries due to AT and NAT regarding incidence, demographics, injury severity, and outcomes. METHODS: A 4-year retrospective review of the Trauma Registry at Children's Medical Center Dallas, a large Level I pediatric trauma center, comparing incidence, age, race, trauma activation, intensive care unit (ICU) need, Injury Severity Score (ISS), and mortality between AT and NAT patients was carried out. RESULTS: There were 5948 admissions, 92.5% were AT and 7.5% were NAT victims. The NAT patients were younger (1.8 ± 3.3 years vs. 6.8 ± 4.2 years for AT patients; p < 0.01), more often required an ICU stay (NAT 36.5% vs. 13.8% for AT patients; p < 0.0001), and had a higher ISS 14.0 ± 9.7 vs. 7.5 ± 7.2; p < 0.0001). The mortality rate in NAT was 8.9% vs. 1.4% for AT (p < 0.001). Of the 40 NAT patients who ultimately died, 17.5% were not initially diagnosed as NAT. CONCLUSIONS: NAT victims differ significantly from the AT patients, with a greater severity of injury and a 6-fold higher mortality rate. Delayed recognition of NAT occurred in almost 20% of the cases. It is generally accepted that NAT is underestimated. Its increased mortality rate and severity of injury are also not well recognized compared to the typical pediatric trauma child.

Impact of surgical approach on outcome in 622 consecutive pyloromyotomies at a pediatric teaching institution.

PURPOSE: The aim of this study is to compare the outcome of 3 different approaches to pyloromyotomy in a large single institution series. METHODS: Records of consecutive patients undergoing pyloromyotomy for an 8-year period were reviewed. Patients' age, sex, weight, operating time, length of stay, number of emeses, and complications were recorded. Variables were compared between right upper quadrant (RUQ), umbilical (UMB), and laparoscopic (LAP) approaches. RESULTS: Six hundred twenty-two patients were included in the study. Operating time was significantly shorter for LAP and RUQ compared to UMB. Length of stay did not differ between the groups. There were fewer episodes of emesis in the LAP group. There was a trend toward a higher rate of complications in UMB group. CONCLUSION: Outcomes after pyloromyotomy are institution dependent and cannot be generalized. Patient safety is the first concern, followed by patient comfort and cosmesis. Laparoscopic pyloromyotomy can be as fast and efficient as open, without an increased rate of complications, with excellent cosmetic results, and less analgesic requirement. If skill and experience to replicate good outcomes of laparoscopy are not available, open pyloromyotomy is a safer technique. The UMB approach is an alternative method to achieve good cosmesis without laparoscopy in the hands of a surgeon proficient in this method.

Complete colonic duplication--a case report.

Duplications of the entire colon are very rare. An 18-month-old boy presented with symptoms of chronic constipation and was noted with a complete colonic duplication. The presentation and management are discussed.

A comparative analysis of cartilage engineered from different perinatal mesenchymal progenitor cells.

We sought to compare engineered cartilaginous constructs derived from different perinatal mesenchymal progenitor cell (MPC) sources. Ovine MPCs isolated from amniotic fluid (AF, n = 8), neonatal bone marrow (BM, n = 6), and preterm umbilical cord blood (CB, n = 12) were expanded and comparably seeded onto synthetic scaffolds. Constructs were maintained in chondrogenic media containing transforming growth factor-beta. After 12-15 weeks, specimens were compared with native fetal hyaline and elastic cartilage by gross inspection, histology, immunohistochemistry, and quantitative extracellular matrix (ECM) assays. MPCs from AF proliferated significantly faster ex vivo when compared to MPCs from the other sources. Chondrogenic differentiation was evident in all groups, as shown by toluidine blue staining and expression of aggrecan, cartilage proteoglycan link protein, and collagen type II. Quantitatively, all engineered specimens had significantly lower levels of glycosaminoglycans than native hyaline cartilage. Elastin levels in AF-based constructs (156.0 +/- 120.4 microg/mg) were comparable to that of native elastic cartilage (235.8 +/- 54.2 microg/mg), both of which were significantly higher than in BM- and CB-based specimens. We conclude that the ECM profile of cartilage engineered from perinatal MPCs is highly dependent on cell source. ECM peculiarities should be considered when designing the optimal cartilaginous bioprosthesis for use in perinatal surgical reconstruction.

Survey of pediatric surgeons on current practices of bowel preparation for elective colorectal surgery in children.

BACKGROUND: Guidelines regarding bowel preparation exist for the adult but not the pediatric population. Our aim was to evaluate the bowel preparation practices, including antibiotic usage for elective colorectal operations in children. METHODS: A survey was designed and administered to a nationwide group of pediatric surgeons to ascertain current practices of bowel preparation. RESULTS: Four hundred ninety-three surveys were administered, and 136 physicians responded (28%). Mechanical bowel preparation was used by 96% of the respondents. Preoperative intravenous antibiotics were used by 99% of respondents. The number of years in practice did not significantly affect the use of oral antibiotics (P = .62) or the duration of intravenous antibiotics (P = .78). CONCLUSIONS: There is a wide variation in bowel preparation practices in children. A prospective, randomized trial would be helpful to identify the role of oral antibiotics and optimal duration of intravenous antibiotics in this population.

Postnatal myocardial augmentation with skeletal myoblast-based fetal tissue engineering.

BACKGROUND: Cardiac anomalies constitute the most common birth defects, many of which involve variable myocardial deficiencies. Therapeutic options for structural myocardial repair remain limited in the neonatal population. This study was aimed at determining whether engineered fetal muscle constructs undergo milieu-dependent transdifferentiation after cardiac implantation, thus becoming a potential means to increase/support myocardial mass after birth. METHODS: Myoblasts were isolated from skeletal muscle specimens harvested from fetal lambs, labeled by transduction with a retrovirus-expressing green fluorescent protein, expanded in vitro, and then seeded onto collagen hydrogels. After birth, animals underwent autologous implantation of the engineered constructs (n = 8) onto the myocardium as an onlay patch. Between 4 and 30 weeks postoperatively, implants were harvested for multiple analyses. RESULTS: Fetal and postnatal survival rates were 89% and 100%, respectively. Labeled cells were identified within the implants at all time points by immunohistochemical staining for green fluorescent protein. At 24 and 30 weeks postimplantation, donor cells double-stained for green fluorescent protein and Troponin I, while losing skeletal (type II) myosin expression. CONCLUSIONS: Fetal skeletal myoblasts engraft in native myocardium up to 30 weeks after postnatal, autologous implantation as components of engineered onlay patches. These cells also display evidence of time-dependent transdifferentiation toward a cardiomyocyte-like lineage. Further analysis of fetal skeletal myoblast-based constructs for the repair of congenital myocardial defects is warranted.

Fetal hepatic haematopoiesis is modulated by arterial blood flow to the liver.

We describe an as yet unrecognised relationship between fetal hepatic haematopoiesis and arterial blood flow to the liver. To increase hepatic arterial flow, the common bile duct (CBD) was ligated in fetal lambs. Reduction of hepatic arterial flow was accomplished in age-matched animals by hepatic artery (HA) ligation. Multiple analyses performed before term showed a significant increase in haematopoietic cell density in CBD animals when compared with sham controls and HA animals. In contrast, HA animals demonstrated a decrease in liver haematopoietic activity. Fetal hepatic haematopoiesis is dependent upon arterial blood flow to the liver.

Diaphragmatic repair through fetal tissue engineering: a comparison between mesenchymal amniocyte- and myoblast-based constructs.

PURPOSE: We have previously shown that fetal tissue engineering is a preferred alternative to diaphragmatic repair in a large animal model. This study was aimed at comparing diaphragmatic constructs seeded with mesenchymal amniocytes and fetal myoblasts in this model. METHODS: Neonatal lambs (n = 14) underwent repair of an experimental diaphragmatic defect with identical scaffolds, either seeded with labeled autologous cells (mesenchymal amniocytes in group 1 and fetal myoblasts in group 2) or as an acellular graft (group 3). At 1 to 12 months postoperatively, implants were harvested for multiple analyses. RESULTS: Repair failure (reherniation or eventration) was significantly higher in group 3 than in groups 1 and 2, with no difference between groups 1 and 2. Seeded fetal myoblasts quickly lost their myogenic phenotype in vivo. All grafts contained cells with a fibroblastic-myofibroblastic profile. Elastin concentrations and both modular and ultimate tensile strengths were significantly higher in group 1 than in groups 2 and 3. There were no differences in glycosaminoglycans and type I collagen levels among the groups. CONCLUSIONS: Diaphragmatic repair with a mesenchymal amniocyte-based engineered tendon leads to improved structural outcomes when compared with equivalent fetal myoblast-based and acellular grafts. The amniotic fluid is a preferred cell source for tissue-engineered diaphragmatic reconstruction.

Hydrogel optimization for cultured elastic chondrocytes seeded onto a polyglycolic acid scaffold.

The purpose of this study was to compare the effect of different hydrogels on the production of tissue-engineered cartilage based on polyglycolic acid (PGA). Chondrocytes were isolated from adult sheep auricles. Alginate, Type I collagen, methylcellulose, and pluronic F127 hydrogels were evaluated, as were controls prepared without hydrogels. Proliferated chondrocytes were mixed with each hydrogel at 20 x 10(6) cells/mL and seeded onto PGA (1 x 1 x 0.2 cm, n = 60). The constructs were cultured with serum-free medium containing 5 ng/mL TGF-beta(2) and 5 ng/mL des(1-3)IGF-I in rotational bioreactors for up to 6 weeks. The cellular morphology, histology, and biochemistry were analyzed. Type I collagen, methylcellulose, and pluronic F127 displayed improved cartilage matrix deposition in terms of histology and biochemistry compared to alginate. It was not concluded that the combined seeding of chondrocytes and hydrogels on a PGA scaffold had significantly better effects than cell seeding without hydrogels. However, the histology and other useful findings in this ECM analyses suggested that Type I collagen and MC hydrogels were the best candidates for cartilage regeneration, because of their stimulation for chondrocyte proliferation in a three-dimensional culture as well as cartilage regeneration.

In vitro cartilage regeneration from proliferated adult elastic chondrocytes.

The purpose of this study was to investigate cellular feasibility in the proliferation and differentiation status of adult chondrocytes for cartilage regeneration in comparison to fetal chondrocytes. Primary cells were isolated from adult (n = 6) and fetal (n = 6) sheep ear cartilages and expanded in 10% fetal bovine serum (FBS) containing Ham's F12 medium, in which adult and fetal cell proliferation rates were compared using a WST-1 assay kit. Approximately 4 million cells were seeded onto each 1 x 1 x 0.2-cm (200 microL) nonwoven fabric scaffold made from polyglycolic acid. Cell/polymer constructs were cultured in serum-free DMEM/F12 medium supplemented with 5 ng/mL TGF-beta2 and 5 ng/mL des(1-3)IGF-I (adult chondrocytes, group A) or in 10% FBS containing Ham's F12 medium (adult chondrocytes, group B, and fetal chondrocytes, group C) as controls in a rotating bioreactor for 6 weeks. The proliferation assay showed that fetal cells had a significantly better growth potential than did adult cells. Histology and extracellular matrix analyses revealed that groups A and C qualitatively displayed better matrix deposition than did group B. In conclusion, although adult sheep elastic chondrocytes had less growth potential than did fetal cells, the serum-free medium supplemented with growth factors significantly enhanced the production of cartilage matrix secreted from proliferated adult sheep elastic chondrocytes.

Cartilage engineering from ovine umbilical cord blood mesenchymal progenitor cells.

We aimed to determine whether three-dimensional (3D) cartilage could be engineered from umbilical cord blood (CB) cells and compare it with both engineered fetal cartilage and native tissue. Ovine mesenchymal progenitor cells were isolated from CB samples (n=4) harvested at 80-120 days of gestation by low-density fractionation, expanded, and seeded onto polyglycolic acid scaffolds. Constructs (n=28) were maintained in a rotating bioreactor with serum-free medium supplemented with transforming growth factor-beta1 for 4-12 weeks. Similar constructs seeded with fetal chondrocytes (n=13) were cultured in parallel for 8 weeks. All specimens were analyzed and compared with native fetal cartilage samples (n=10). Statistical analysis was by analysis of variance and Student's t-test (p<.01). At 12 weeks, CB constructs exhibited chondrogenic differentiation by both standard and matrix-specific staining. In the CB constructs, there was a significant time-dependent increase in extracellular matrix levels of glycosaminoglycans (GAGs) and type-II collagen (C-II) but not of elastin (EL). Fetal chondrocyte and CB constructs had similar GAG and C-II contents, but CB constructs had less EL. Compared with both hyaline and elastic native fetal cartilage, C-II and EL levels were, respectively, similar and lower in the CB constructs, which had correspondingly lower and similar GAG levels than native hyaline and elastic fetal cartilage. We conclude that CB mesenchymal progenitor cells can be successfully used for the engineering of 3D cartilaginous tissue in vitro, displaying select histological and functional properties of both native and engineered fetal cartilage. Cartilage engineered from CB may prove useful for the treatment of select congenital anomalies.

Intratracheal pulmonary ventilation improves gas exchange during laparoscopy in a pediatric lung injury model.

BACKGROUND/PURPOSE: This study was aimed at determining whether intraoperative intratracheal pulmonary ventilation (ITPV) could prevent/treat respiratory complications of laparoscopy in a model of pediatric pulmonary insufficiency. METHODS: Severe lung injury was induced in 0- to 2-month-old lambs (n = 5) by endotracheal saline lavage. Animals then underwent establishment of CO2 pneumoperitoneum. Intraperitoneal pressures were progressively raised from 0 to 15 mm Hg, at intervals of 5 mm Hg. At each interval, blood gas and hemodynamic data were recorded, 20 minutes after initiation of both conventional ventilation and pure ITPV. All ventilatory parameters were constant and identical on both modes of ventilation. RESULTS: On conventional ventilation, severe respiratory acidosis and hypoxemia ensued at intraperitoneal pressures of 5 mm Hg and 10 mm Hg or more, respectively. Compared with conventional ventilation, ITPV led to statistically significant decreases in PCO2 at intraperitoneal pressures of 5 mm Hg (43.2 +/- 5.2 vs 56.1 +/- 6.6 mm Hg) and 10 mm Hg (45.1 +/- 3.2 vs 61 +/- 6.3 mm Hg) and to significant increases in PO2 at 10 mm Hg (92 +/- 10.2 vs 61 +/- 8.1 mm Hg), resolving the acidosis and hypoxemia at those pressure levels. CONCLUSIONS: Compared with conventional ventilation, ITPV improves both CO2 removal and oxygenation during CO2 pneumoperitoneum in a pediatric lung injury model. Intratracheal pulmonary ventilation may be a safer intraoperative mode of ventilation for neonates and children with respiratory failure who require laparoscopy.

Cost considerations and applicant characteristics for the Pediatric Surgery Match.

BACKGROUND/PURPOSE: Formal training in pediatric surgery is highly competitive. The limited number of accredited positions has historically favored applicants with basic science experience, numerous publications, national presentations, and exposure to well-known pediatric surgeons. This review analyzes characteristics of successful applicants and cost associated with the Match. METHODS: A survey was e-mailed to 45 applicants after the 2003 Match. Geographic provenance, demographics, qualifications, costs, and valued program characteristics were assessed. Statistics were formulated by chi2 and Student's t test. RESULTS: Thirty-six applicants (80%) responded. Successful characteristics for matched vs unmatched included number of publications, 11.2 vs 5.7 (P < .01); first-author designation, 6.4 vs 3.1 (P = .02); basic science papers, 5.7 vs 1.7 (P < .01); national presentations, 5.8 vs 2.4 (P = .02); and presentations at pediatric surgical meetings, 2.0 vs 0.6 (P = .04). Ninety percent of matched applicants took time off to perform basic science research (P < .01). Average candidate expense was $6974, which represented 14% of pretax salary. Forty-one percent of applicants noted that cost limited the number of interviews taken. Fifty percent preferred a regional interview process to limit expense. Candidates ranked case diversity, volume, and mentor's advice as the most valued program characteristics. Successful applicants matched at their fifth rank on average. Eighty-six percent of unsuccessful applicants will reapply. CONCLUSIONS: Results of this study are important to those interested in the future of pediatric surgery. Successful applicants were shown to have several national presentations and multiple scientific publications, especially in basic sciences. Applicant costs are high, totaling more than $236,000 for survey respondents.

Diaphragmatic reconstruction with autologous tendon engineered from mesenchymal amniocytes.

PURPOSE: This study examined the effects of amniocyte-based engineered tendons on partial diaphragmatic replacement. METHODS: Ovine mesenchymal amniocytes were labeled with green fluorescent protein (GFP), expanded, and seeded into a collagen hydrogel. Composite grafts (20 to 25 cm2) based on acellular dermis (group I), or acellular small intestinal submucosa (group II) received either a cell-seeded or an acellular hydrogel within their layers. Newborn lambs (n = 20) underwent partial diaphragmatic replacement with either an acellular or a cellular autologous construct from either group. At 3 to 12 months' postoperatively, implants were subjected to multiple analyses. RESULTS: Diaphragmatic hernia recurrence was significantly higher in animals with acellular grafts (5 of 5) then in animals with cellular ones (1 of 4) in group I (P <.05) but not in group II (3 of 6 and 4 of 5, respectively). Cellular grafts had higher modular (5.27 +/- 1.98 v. 1.27 +/- 0.38 MPa) and ultimate (1.94 +/- 0.70 v. 0.29 +/- 0.05 MPa) tensile strength than acellular implants in group I (P <.05), but not in group II. Quantitative analyses showed no differences in extracellular matrix components between cellular and acellular implants in either group. All cellular implants showed GFP-positive cells. CONCLUSIONS: Diaphragmatic repair with an autologous tendon engineered from mesenchymal amniocytes leads to improved mechanical and functional outcomes when compared with an equivalent acellular bioprosthetic repair, depending on scaffold composition. The amniotic fluid may be a preferred cell source for engineered diaphragmatic reconstruction.

Massive iliac artery bleeding in patients receiving intraoperative radiation therapy for advanced rectal cancer: report of two cases.

Multimodality treatment for advanced rectal cancer, including intraoperative radiation therapy, is associated with significant complications. Unfortunately, because of the high local recurrence rates and mortality in these patients, the treatment regimen of external beam radiation therapy, chemotherapy, extensive resection, and intraoperative radiation therapy is one of the few potentially curative options available. Here we report two cases of massive iliac artery bleeding after multimodality treatment for advanced rectal cancer, which included intraoperative radiation therapy.

Management of spontaneous colonic perforation in Ehlers-Danlos syndrome type IV.

A 14-year-old girl with a family history of fatal colonic rupture, presented with a 2-day history of abdominal pain and signs of peritonitis. At laparotomy, a full-thickness perforation of the sigmoid colon was found, which was exteriorized as a loop colostomy. Subsequently, molecular studies of the patient's cultured fibroblasts found a point mutation in the COL3A1 gene, confirming a diagnosis of Ehlers-Danlos syndrome type IV (EDS-IV). Four and a half years later, a total abdominal colectomy and ileoproctostomy were performed, restoring intestinal continuity. At 5 years follow-up, the patient has had no further complications. Although spontaneous colonic perforation is a well-reported manifestation of EDS-IV, a consensus on the surgical management of this complication in EDS-IV has yet to be determined. Given the high rate of reperforation in EDS-IV when the colon is left in place and the low incidence of reported small bowel and rectal perforations, subtotal colectomy is a reasonable treatment. Primary anastomosis and avoidance of an end-ileostomy was possible in this young patient, with no evidence of anastomotic leakage nor reperforation to date. Lifelong close follow-up should be continued in these patients, because the natural history of this anatomy in EDS-IV is not known.

Fetal tissue engineering: in vitro analysis of muscle constructs.

BACKGROUND/PURPOSE: This study was aimed at examining the impact of different tissue engineering techniques on fetal muscle construct architecture. METHODS: Myoblasts from ovine specimens of fetal skeletal muscle were expanded in culture and their growth rates determined. Cells were seeded at different densities onto 3 scaffold types, namely polyglycolic acid (PGA) treated with poly-l-lactic acid (PLLA), a composite of PGA with poly-4-hydroxybutyrate (P4HB), and a collagen hydrogel. Constructs were maintained in a bioreactor and submitted to histologic, scanning electron microscopy, and DNA analyses at different time-points. Statistical analysis was by the likelihood ratio and paired Student's t tests (P <.05). RESULTS: Fetal myoblasts proliferated at faster rates than expected from neonatal cells. Cell attachment was enhanced in the PGA/PLLA matrix and collagen hydrogel when compared with the PGA/P4HB composite. Necrosis was observed at the center of all constructs, directly proportional to cell seeding density and time in the bioreactor. CONCLUSIONS: Fetal myoblasts can be expanded rapidly in culture and attach well to PGA/PLLA, as well as collagen hydrogel but less optimally to PGA/P4HB. Excessive cell seeding density and bioreactor time may worsen final construct architecture. These findings should be considered during in vivo trials of muscle replacement by engineered fetal constructs.